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Old Oct 21, 2005, 11:13 PM
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micro_builder's Avatar
United States, TX, Fort Worth
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An EDF Proposition

hi guys,

we had a little family gathering tonight so i got a chance to talk to my step dad about something i've had in mind for a while. he owns a machine shop, does a lot of CNC milling, ect. i showed him a few pictures of the EDFs being built around here and in the EDF forum and asked him if his CNCs could make something similar.

he said his machines could do it, but he would need some exact measurments, CAD drawings would be ideal. then he could figure out how much time/money it would cost to do some. this is where you guys come in. i dont know enough about EDFs to say what would be the most efficient impeller, number of blades, pitch, ect. i also dont have any CAD experience. but, i do know that a good handfull of people here know a good amount of EDF info and have CAD skills.

sooo, with that said, if there's enough people interested, and someone who would be willing to draw some CAD designs of some a few differant EDF designs, he might be able to make some and we could sell them - then we'd finally have some fans for our 7mm and maybe even 6mm motors. i'm not looking to try to make a buisness out of this, i could afford to have a few made just for myself, but i figure if others are interested, why not share?

some questions though. what size of EDF would be wanted, size of motors, number of blades, pitch of blades, cost you'd be willing to spend for one? all this aside, i dont know if he'll be able to do it anyway, he's running a business and may not have time to use his machines for something like this, but i thought i'd run it past you folks just in case. once i get some feedback from you guys i can talk to him again and we can try to figure something out from there.

any thoughts?

nick
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Old Oct 22, 2005, 11:14 AM
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USA, IN, Greenwood
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No CAD, or CAD experience here, but,this is a curious undertaking, I bet it generates some interest. Im wondering what material you would use for this. Wow, an impeller for a 6mm motor would be quite small huh? Good luck, Im thinking there will be a finished product, I cant wait to see it!
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Old Oct 22, 2005, 12:35 PM
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carbon fiber cloth or fiberglass is probably the best material for both the impeller and the housing since its light and tough and holds its shape well.
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Old Oct 22, 2005, 12:36 PM
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what would also be great is to find a motor that would generate great thrust with just 1 cell.
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Old Oct 22, 2005, 12:43 PM
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United States, TX, Fort Worth
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hi guys.

yeah, i had forgotten to ask what might be the best material to use. nylon? i really dont know, but i'm pretty sure he's got differant types of plastic at the shop. i'm pretty sure his machines could do 7mm size ones, but we'll have to see on the 6mm's. though that would be great. i do know that EDFs like a high RPM, so maybe that purple super slick motor would work, 30k RPM rating! if all else fails and this doesnt go anywhere, i'll have a few made for myself and stick them in a plane. maybe i'll do that first just to make sure it'll be worth it for everyone else too.

nick
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Old Oct 22, 2005, 02:53 PM
It's a spiderweb of knit lines
Souderton Pa. USA
Joined Mar 2002
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Hi Nick,
Probably the best use of CNC equipment would be to make a mold so carbon rotors could be made from the mold. A highly polished rod of the correct size would work for the duct. I have been working on a brushless motor taylored to the Kokam 145 mAh li-poly. That battery can handle just over 1 amp and seems to me to be able to handle the most draw per a gram of any available in the 1 amp class.

Rotor design will be a real challenge! Probably best to start with the blade design from the surplus fans here: http://www.rcgroups.com/forums/showthread.php?t=380439
then reduce the hub and blade count to suit the motor diameter.

Many have tried, some claim success, a few have posted video. I'm still trying.
Mike
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Old Oct 22, 2005, 07:14 PM
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hi Mike,

good idea on using the CNCs for mold making, i'll pass that along to my step dad as well.

i did a search for EDFs here in this forum and ran across that thread you posted. the picture of the little impellor on the M20 looks like a nice size, i checked the website linked to them and they're still in stock so i might pick one up for some reference. i wonder if the overall performance would increase if it had a rounded nose on the hub.

i think if things go well, i'm going to try for a 5 blade rotor to start with, make a few of them with differant pitches and test them. i guess that means i'll finally get around to building that thrust stand i really hope this works out, even if no one else is interested, i know quite a few planes that i'd really like to have a true scale look to them (no prop!)

nick
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Old Oct 22, 2005, 09:29 PM
It's a spiderweb of knit lines
Souderton Pa. USA
Joined Mar 2002
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Hey Nick,
I'm sure there will be lots of people interested. I think hopes have been raised and dashed by so many (me included) that people are a bit skeptical and rightfully so. It will someday be common. There is a lot of work going on in this area, and in a variety of sizes. I'd be interested in a mold if you come up with something.
Mike
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Old Oct 22, 2005, 10:38 PM
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hi Mike,

i understand what you're saying about peoples hopes getting up and then being dashed. i didnt want to get anyones hopes up, just in case it didnt work out, but i needed help from folks here in order to get things going - CAD drawings and other EDF info, ect. maybe i'll just lend him a 3 blade impellor i have and see if he can just scale it down and work from there. it may be a slow process, but i feel good about something worthwhile coming from it eventually. time will tell, i'll see him this week and work some things out to get started.

nick
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Old Oct 22, 2005, 10:59 PM
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United States, MI, Temperance
Joined Sep 2002
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I've been watching for a micro EDF solution for quite some time. Success has been very limited and all hand made one-off impellers AFAIK. There's a micro EDF Vampire video posted somewhere that does a pretty darn good job. Hopes are dashed when no additional info can be found.

I haven't been impressed with the durability of pager motors on props. I doubt one would last long in an EDF setup. The M20 would prob. have a useful life. The micro brushless would prob. be even better. I think EDF is a case where the micro brushless is needed.

There's a micro MIG-15 in my hangar as soon as I can lay hands on a micro EDF setup that is known to work. One or Two cells and drawing less than 1.5A.
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Old Oct 22, 2005, 11:50 PM
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Nick - do you have a 1 cell BL esc?
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Old Oct 23, 2005, 12:19 AM
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hi Tim,

i agree, a BL powered EDF would probably work best, but being able to use the readily available, and cheaper, 7mm SS motors would allow more people to get into it i think. i really cant speculate on how things will go, but idealy, we'd eventually get to BL rotors as well.

hi nitro, nope, no BL controllers yet. i do have a rather small (12mm i believe) hard drive bl motor that will be used eventually. but, DU's equipment is on my list of things to get though for sure - i have a 8" micro mite waiting in the wings to be a 4 channel BL screamer.

nick
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Old Oct 23, 2005, 07:39 AM
It's a spiderweb of knit lines
Souderton Pa. USA
Joined Mar 2002
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Most of the available BL are outrunners and as such they take up a lot of hub room, this pushes the diameter up to or over 1 inch. It would need a special wind, most likely, to bring up the Kv. That's why I've been working on an in runner. Problem is parts aren't readily available, lots of custom parts need to be made and that gets expensive and/or time consuming. The DWE BL-1 will be required, at .5 grams it has yet to be beat.

Yes, Nick, a rounded cone on the fan will help a lot. When I get some more of those fans I'll probably vacuum form some, want some?

Mike
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Old Oct 23, 2005, 11:39 AM
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Mike,

yeah, that would be great, thanks for the offer. did you ever find a max RPM for those little things?

last night i did a LOT of reading. doing a search in this forum for EDF brought me back 250 somethin results. i got through about 15 differant threads and made it to page 14 on the KP00 fan unit construction thread before my eyes started to burn. i got a lot of good info, enough to give me a basis to tell my step dad at least. i'm thinking a 20-25mm impellor, 3 blades @ 45 degrees, rounded nose, and hopefully a milled duct with built in angled stator veins, rounded intake lip, and a rear cone for the end of the motor.

i'm heading to my parents again tonight, so i'll bring all this info to my step dad and i'll also be bringing along a 3 blade impellor i have from a jet, its just under 50mm. i have to remember to ask him what type of plastics he has there.

nick
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Old Oct 23, 2005, 02:22 PM
It's a spiderweb of knit lines
Souderton Pa. USA
Joined Mar 2002
2,638 Posts
Nick, the manufacturer will not cooperate knowing the use we have in mind. Their statement was that "they are safe when used in our housings with our motors." LOL They also claimed to not make the one's for sale as surplus.
Mike

Edit: The manufacturer I was speaking with do not make the surplus rotors.
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Last edited by mcross; Oct 26, 2005 at 06:55 PM.
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